Patterns are created on substrates for a variety of applications, such as during the manufacture of optical and magnetic data storage media, semiconductor integrated circuits (ICs), biomedical devices, etc. Depending upon the processing involved, a substrate may be subjected to multiple steps using different types of equipment.
These and other forms of processing may involve mounting the substrate in a recording system such as but not limited to an electron beam recorder (EBR), a laser beam recorder (LBR), etc. In a rotatable type recording system, the substrate is rotated by a support mechanism (sometimes characterized as a “turntable”) about a central axis and subjected to a recording beam that writes a recorded pattern to the substrate. In a raster type recording system, the substrate is mounted to a support mechanism (sometimes characterized as a “fixed reference table”) and held in a stationary position as a recording beam is advanced across the substrate to write a recorded pattern. The recorded pattern can take the form of any number of linear or circumferentially arranged features including data bits, semiconductor elements, bar codes, images, holograms, three dimensional (3D) structures, etc.
The formation of multi-layer features may require the substrate to be mounted in the recording system, or in other recording systems, multiple successive times to generate features in different layers of the substrate. The substrate may be removed between successive passes for other processing (e.g., metallization, cleaning, chemical or physical vapor deposition, etc.), requiring the substrate to be re-mounted each time a new recording pass is applied.
It can be seen that multi-layer processing requires adequate registration (alignment) of the substrate with a known reference point such that newly written features align with previously recorded features on the substrate. Alignment techniques of the existing art are often inadequate to achieve the requisite registration of the substrate. This is because the relative angular and translational positions of the substrate and the support mechanism will tend to be different for each mounting of the substrate, so the exact centering of the substrate on the support mechanism will tend to be offset for each mounting of the substrate.